Dental-porcelain color matching system

ABSTRACT

A dental-porcelain color matching system comprises a plurality of dental-porcelain beads arranged in a closely spaced manner on a common support so that their colors vary in an ordered manner. The beads are carried at the ends of arms which are either flexible or pivotable on a main trunk of the support so that a bead to be located against a patent&#39;s natural tooth for color comparison therewith can be moved away from other beads on the support to avoid color interference therefrom. Additional beads provided have varying translucent enamels on opaque porcelain bases to allow the color, translucency and depth of enamel of a patient&#39;s teeth to be gauged. The beads also vary in shape from that of an unworn natural incisor tooth with a ridged cutting edge to that of a worn incisor tooth with a smooth cutting edge.

BACKGROUND OF THE INVENTION

The present invention relates to a colour-matching system particularlyfor use in matching the colour of a dental prosthesis to that of anadjacent tooth.

In this specification the term colour will be used to include thedifferent hues, such as red, yellow, green and orange, and alsodifferent tints or shades of the various hues in which the pure hue ismodified by the admixture of white and/or black pigment in varyingdegrees.

Although the predominant hue of natural teeth is yellow, the variationsbetween a very pale cream and greyish brown are infinite and dentalporcelains are now available in a wide variety of different colours inorder to allow dental prostheses to be matched closely to the colour ofadjacent teeth in a patient's mouth. This colour matching is generallyeffected with the aid of samples of the different coloured porcelains,each provided in the form of a tiny bead, or button, on a respectivespatula-like carrier. These are placed successively in a patient'smouth, close to a tooth which will be adjacent the prosthesis whenfitted, until a good colour match is found.

A problem with this known system is that the multitude of spatulasneeded occupies considerable bulk and is not easy to store in a simplesystem which allows them to be replaced in order quickly after use.Indeed, the normal practice is for a dental surgeon to remove severalspatulas from the system at a time and to put them down temporarily onany convenient surface; the spatulas inevitably get muddled andconsiderable time is wasted in sorting and replacement in the systemafter use.

A further difficulty with the use of spatulas is that they are normallystiff and opaque so that it is not easy to locate them in the patient'smouth, close enough to a tooth for colour matching, without alsoobstructing the light to the tooth. In this respect, the problems oflighting a patient's mouth and the effects on colour perception of evenslight shadows are well known.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a range of dentalporcelain samples for colour matching in a form which is more convenientto use than current systems.

Accordingly, the present invention provides a dental-porcelaincolour-matching system comprising a plurality of dental porcelain beadsof different colours carried on a support adapted to allow beads to bemoved apart so that each bead can be placed individually against apatient's natural tooth without colour interference from any other beadon the support.

In order for the beads to be movable relative to each other they may bemounted on a flexible and/or resilient support, preferably of plasticsmaterial, or the support may be formed in several interengaged partswhich are movable relative to each other. They may, for example, bemutually telescopic or pivotable. Whatever form of movement is allowed,the beads may be located very close together (of the order of a few mmor even touching in some embodiments) in the rest or stored condition ofthe system so that the overall bulk of the stored system may be lessthan that of a spatula system having the same number of beads.

The beads may be releasable from the support, or individual beads orgroups of beads may be carried on support parts releasably engageablewith the main body of the support, so that beads may be interchangeableto vary the colour range provided in a system but, during use by thedental surgeon, the beads are preferably retained on the common supportso that they cannot get mixed up; this relieves the surgeon or histechnician of the time-wasting task of sorting after use.

The beads themselves may be of the usual button shape, about 3 mm to 8mm in diameter, or of other convenient shape such as pear or toothshape. From about 8 to 60 beads may conveniently be provided on any onesupport, additional supports being provided for further beads, ifrequired.

The beads are preferably arranged in an ordered manner in terms ofgradation of colour, the arrangement depending on the shape of thesupport; three-dimensional arrangements are certainly possible althoughessentially two-dimensional arrays, which enable all the beads to beseen to facilitate selection by the dental surgeon, are preferred. Inthe case of flexible supports without interengageable parts,two-dimensional arrangements are particularly convenient since thesupport may then be made simply and cheaply in sheet form, preferablyfrom sterilizable, washable plastics material. In such cases the supportis preferably branched, beads being carried on the branches which may bemoved apart to facilitate the location of individual beads against atooth in use.

Beads may also be located on the trunk, or spine, of the support or onfingers projecting into apertures or spaces on or adjacent the spine andflexible out of the plane of the spine to allow colour comparison ofrespective beads with a tooth.

In alternative embodiments in which the support has interengaged partswhich are movable relative to each other, the support may also have aspine and arms extending therefrom to support beads at their free ends.In a preferred embodiment, each arm is pivotable relative to the spinefrom a stored position in which it lies alongside the spine and adjacentother arms to a position of use in which it projects from the spine andits button is sufficiently spaced from other buttons for comprison witha tooth. Each arm may be pivotable individually or combined in a groupwith other arms pivotable as a group.

In embodiments with interengaged parts, these may be made from the sameor different materials. A spine part may, for example, be of metal,preferably stainless steel or brass, or of plastics material(thermosetting or thermoplastics) and is preferably sufficiently thickto be fairly rigid. The arms, on the other hand, are preferably ofplastics material, and may be rigid or flexible or possibly of graduatedthickness such that the end attached to the spine is relatively rigidwhile the free end carrying the bead is fairly flexible.

The support, or central part of the support, of the present inventionmay be opaque but at least the parts carrying the beads are preferablytransparent or translucent to minimize the obstruction of light to apatient's mouth, in use. A translucent material is preferred since thismay be white, or an extremely pale colour, to provide a convenientbackground which facilitates the colour matching of a bead with a tooth.Each bead on a support is preferably identified by a reference which maybe printed on, glued to or otherwise provided on or adjacent therespective bead on the front or reverse side of the support.

The beads may be attached to the support in any convenient manner; forexample they may be snap-engageable with the support, glued to thesupport or embedded in it during manufacture of the support.

If a crowned tooth having a metal core is to be made, the porcelainbeads are preferably metal-backed to facilitate and improve the colourmatching achievable. The backing may comprise a thin foil or a metalplate, stud or rivet by which the bead can be attached to the support.The bead is preferably glued to the metal.

The beads themselves may also comprise several porcelain layers ofdifferent colours since both teeth and modern dental prostheses includeseveral layers. In particular, the system of the invention may furtherinclude a set of beads comprising different thicknesses of substantiallycolourless, transparent or translucent ceramic, simulating dentalenamel, over an opaque base to facilitate the matching of the enamelthickness in a dental prothesis with that of the patient's teeth. Inthis case, the beads are preferably generally tooth shaped and thetransparent layers may be formed to simulate different stages in thewear of natural teeth.

A further set of beads may also be provided, each bead comprising anopaque dental-porcelain base with a coating of translucent enamel, theenamel coating of the beads varying in translucency and/or colour sothat the beads may be compared with a natural tooth to obtain anestimate of the translucency and/or colour of the tooth enamel for themaking of a dental prosthesis.

Sets of dental-porcelain beads displaying different enamel layers asindicated above, are not themselves known and can be incorporated in anydental-porcelain colour-matching system.

BRIEF DESCRIPTION OF THE DRAWINGS

Several embodiments of the invention will now be more particularlydescribed, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is a top plan view of a dental-porcelain colour matching systemaccording to a first embodiment of the invention;

FIG. 2 is a cross-sectional view, on an enlarged scale, taken on lineII--II of FIG. 1;

FIG. 3 is a top plan view of a second embodiment of a dental-porcelaincolour matching system of the invention with some of the porcelain beadsremoved;

FIG. 4 is a top plan view of part of a third embodiment of adental-porcelain colour-matching system of the invention;

FIGS. 5 and 6 are enlarged sectional views of respective alternativeporcelain beads for use in the systems of FIGS. 3 and 4, taken on a linecorresponding to line V--V FIG. 3.

FIG. 7 is a top plan view of part of a dental colour-matching systemaccording to a fourth embodiment of the invention;

FIG. 8 is a longitudinal-sectional view of part of the system of FIG. 7on an enlarged scale, taken on the line VIII--VIII of FIG. 7.

FIG. 9 is a chart showing a range of dental porcelain colours which maybe displayed with the system of FIGS. 7 and 8; and

FIG. 10 is a top plan view of additional porcelain beads which may beincorporated in the systems of FIGS. 1 to 8.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1 of the drawings, a dental-porcelaincolour-matching system is shown comprising a plurality of button-shapedporcelain beads 1 of different colours carried on one surface, whichwill be termed the upper surface, of a generally-flat, translucent,white, plastics support 2 having a uniform thickness of 2-3 mm. Thebeads are generally designated as 1 and are either beads 1a of the freearms 4 and 5, or beads 16 centrally located. In practice several such"systems" would be provided to display the entire range of dentalporcelain colours available.

The support 2 is moulded from resiliently-flexible silicone rubber orpolyurethane and comprises a central spine 3 with arms 4 and 5projecting from respective opposite sides thereof. The arms 4 and 5 aresubstantially equispaced along the spine 3 and are inclined in oppositedirections to its longitudinal axis, each arm 4 lying substantially on arespective common axis 6 with one of the arms 5. The angle between theaxes 6 and the axis of the spine 3 is conveniently about 60° .

Each arm 4, 5 carries a porcelain bead 1a at its free end and furtherporcelain beads 1b are spaced apart along the spine 3 substantially atthe junction of a pair of arms 4, 5 lying on a common axis 6 with thespine 3. The length of the arms 4, 5 is such that the spacing betweeneach bead 1a and the adjacent bead 1b on the spine and the spacing ofadjacent beads 1b on the spine itself is substantially the same: thebeads 1 are circular, with a diameter of about 8 mm and the distancebetween the centres of adjacent beads 1 is about 17 mm.

In this embodiment there are twelve central beads 1b and eleven on eachof the arms 4 and 5 giving a total of 34 beads. In order to provide aconvenient total of 36 beads 1, two additional arms 7, are provided, oneat each end of the spine 3, the arms 7 projecting from the end arm 4 atone end and from the end arm 5 at the other. This gives the system aconvenient total length of about 190 mm, but clearly any number of beads1 may be provided in such a system on an appropriate length of thesupport 2.

It will be seen from FIG. 4 of the drawings that the cross-section ofthe support 2 widens upwardly: this is to facilitate removal of thesupport from the mould during manufacture. The support is also formedwith rounded corners where the arms 4 and 5 join the spine 3 both tofacilitate moulding and, with the slight narrowing of the spine and armparts not directly carrying the beads, to facilitate flexing of thesupport in its own plane, without tearing, in use.

The beads 1 are attached to the support 2 during moulding, the beadssimply being placed in their correct positions on the upper surface ofthe support before curing of the support. The beads could,alternatively, be glued or otherwise attached to the finished support.

As the beads 1 are located on the support 2, they are arranged in anordered manner in terms of colour. For example, the beads 1 may all beof substantially the same hue, or of closely related hues; beads of moredifferent hues may be provided on additional supports. On eachindividual support the beads will vary in shade or tint, from lighter todarker, in a regular manner.

In particular, in each group of three beads 1 aligned on a common axis6, the central bead 1b may be intermediate in shade between the shadesof the outer beads 1a. The colours of the beads 1 are identified byrespective reference numbers 8 moulded in the undersurface of thesupport 2.

In use of the system described above, a dental surgeon may hold thesupport 2 to place each porcelain bead 1 in turn against a patient'stooth the colour of which is to be matched in the making of a dentalprosthesis. The flexibility of the support allows outer beads 1a on thearms 4 and 5 to be kept out of the way while central beads 1b arelocated against the tooth, bearing in mind the graduated arrangement ofthe colours, however, it may not be necessary to test the central beadcolours and, indeed, these central beads, with the intermediate shades,may be omitted altogether from the system.

It should be noted that the translucent support 2 does not obstructlight entering the mouth substantially and its whiteness allows slightdifferences in colour between a porcelain bead and a tooth being matchedto be perceived. The support may, however, have a slight blue or pinktinge since such a background colour, provided it is not too strong,would enhance the perception of yellow and facilitate the comparison ofclosely matched grey-yellow shades.

It will be appreciated that the system is washable and can besterilized.

With reference now to FIGS. 3 and 4 of the drawings, two alternativedental-porcelain colour matching systems are shown with similar featuresto those of the embodiment of FIG. 1 indicated by the same referencenumerals. These embodiments differ from that of FIG. 1 in the shape ofthe support 2 and in the mode of attachment of the porcelain beads 1 tothe support 2.

In the embodiment of FIG. 3, it will be seen that the central beads 1bare each carried on a finger 9 branching from a respective arm 4 of thesupport 2, the arms 4 being longer than the arms 5. The fingers 9 alllie on the same side of the support spine 3 and project in the samedirection from the arms 4, substantially parallel to the longitudinalaxis of the support 1. Portions 3a of the spine 3 between adjacent arms4 are curved to accommodate the fingers 9.

In the embodiment of FIG. 4, the central spine 3 is broadened comparedwith that of FIG. 1 and formed with apertures 10, the central beads 1bbeing carried on fingers 11 which project into the apertures 10,parallel to the longitudinal axis of the support 2. The arms 4 and 5 arealso arranged in pairs projecting with mirror symmetry one on eitherside of the spine 3.

In use of the embodiments of FIGS. 3 and 4, the central beads 1b can belocated more easily and conveniently against a tooth to be matched thanin the case of the first embodiment of FIGS. 1 and 2.

The beads 1 of embodiments similar to those of FIGS. 3 and 4 could beattached to the support 2 in a similar manner to that shown in FIG. 2but FIGS. 3 to 6 show alternative methods of attachment. For thispurpose, the support arms 4 and 5 and fingers 9 taper towards their endsthen widen into generally-circular pads 12 with circular apertures 13extending from the top to bottom surfaces.

Each bead 1 may be formed with a stem 14 projecting from its undersurface and widening into a head 15, like a press- or collar stud. Thesupport 2 is sufficiently resilient and deformable to allow the head 15,which has a slightly larger diameter than the apertures 13, to be forcedthrough such an aperture 13 and then relaxes slightly to grip the stem14 and retain the bead 1 on the support 2. The entire bead 1 may be madefrom dental ceramics or alternatively, as shown in FIG. 5, the bead 1may have a flat back surface 16 and the stem 14 and the head 15 may bemade from metal with a plate 17 which is glued to the back surface 16 ofthe bead 1, preferably with an epoxy resin.

In the alternative shown in FIG. 6, the bead 1 is glued to a metal plate17 which carries a stem 14 with an axial collar 19 which can be upsetonce the stem 14 has been passed through an aperture 13 to rivet thebead 1 to the support 2.

In the embodiments of FIGS. 3-6, the beads 1 are provided withattachment stems 14 which are offset from their centres, forconvenience, although in alternative embodiments the stems 14 could beplaced centrally.

In the embodiment of FIG. 4, one end of the support 2 has a label 119attached to it in a similar manner to the beads 1 for informationregarding the beads 1 on that support 2.

With reference to FIGS. 7 and 8 of the drawings, a further embodiment ofthe invention is shown in which features similar to those of FIGS. 1 and2 are indicated by the same reference numberal increased by 100.

In FIGS. 7 and 8, a dental porcelain colour-matching system is shownwhich includes a support generally indicated 102 carrying a plurality ofporcelain beads 101. The support 102 is formed in several interengagedparts, the main part comprising an elongate spine 103 having a flat,elongate, rectangular lower surface 123 and a stepped upper surfacedefining approximately square, parallel bearing surfaces 124 inclined ata small angle of about 5° to the lower surface 123. The bearing surfaces124 are approximately 9 mm square and are interconnected by risers 125,approximately 1 mm deep.

The subsidiary parts of the support 102 comprise a plurality ofgenerally flat, straight, support arms, each indicated 104, arranged inidentical groups of four, each generally indicated 126. The four supportarms 104 in each group 126 lie in a common plane and are joined at acommon end 127 from which they extend fanwise, two on each side of aline of mirror symmetry indicated X--X, each arm 104 carrying a dentalporcelain bead 101 at its free end. Each bead 101 may be attached to itssupport arm 104 by any of the methods described above with reference toFIGS. 2 to 6, but the use of a metal backing plate and central rivet(rather than the offset rivet of FIG. 6) is preferred.

Each group 126 is pivotally attached to the spine 103 at the common end127 for pivotal movement in its own plane, each on a respective bearingsurface, or step, 124 on the spine 103. Normally there would be as manygroups 126 in the system as steps 124, but only a few groups are shownin the drawings.

The pivotal attachment of each arm group 126 to a respective step 124 isachieved by means of a pin 128 projecting from the step 124,perpendicular to its surface, and engaged in a through hole 129 in theend 177. The pin 128 has a slightly enlarged head 128a and the hole 129has a widened end seat 129a such that the head 128a is snap engageablethrough the hole 129 in the seat 129a to retain the group 126 on thespine 103. Each group 126 may alternatively carry a pivot pin which isengageable in an aperture in a respective step 124 or may be pivoted onthe step in any other convenient manner, such as by a rivet, and may bepermanently captive on the spine 103 or readily releasable therefrom.

As is best seen in FIG. 7, the pins 128 do not lie along thelongitudinal axis of the spine 103 but are offset to one side of it, allthe pins 128 lying on a single straight line. Similarly, each pivot hole128 is offset to one side of the axis X--X of its arm group 126; eachend 127 is also rounded. This configuration allows each arm group 126 tobe pivoted on its step 124 from a stored position, in which its axisX--X is substantially aligned with the longitudinal axis of the spine103 (as shown by the arm group, indicated 126A, in the left-hand side ofFIG. 7) to a position of use, in which its axis X--X is substantially atright angles to the axis of the spine 103 (as shown by the arm group,indicated 126B, in the right-hand side of in FIG. 7).

As is seen in FIG. 8, when the arm groups 126 are in their storedpositions, they overlap each other and lie on the spine 103 in a verycompact configuration. In their positions of use, however, as shown bythe group 126B in FIG. 7, the free ends of their arms 104 are remotefrom the spine 103 and from the stored groups 126; the arms 104 are ofsuch a length, the two outer arms of the fan being longer than the innerones, that the beads 101 on any one arm group 126 lie on a straightline, indicated by the broken line Z--Z in FIG. 7, which does notintersect the arms 104 of the stored groups 126. In this position ofuse, the dental porcelain beads 101 can be placed against a tooth, thecolour of which is to be matched, without colour interference from anyof the other beads 101 on the support 102.

In the embodiment of FIGS. 7 and 8, the spine 103 is substantially rigidand may be made from metal or plastics material, preferably NYLON(Registered Trade Mark). The arms 104 are preferably of pale-coloured,translucent plastics material for reasons explained earlier in thisspecification. In the embodiment shown, the arms 104 are generally rigidand cannot be flexed in their own plane, but have sufficient flexibilityto be flexed out of this plane to facilitate individual location againsta tooth.

In FIGS. 7 and 8, a spine 103 is shown with twenty-one steps 124 whichcan accommodate the same number of groups 126, giving a total ofeighty-four buttons. These can conveniently be divided into three groupsof twenty-eight buttons displaying different dental-porclain colours, asindicated in FIG. 9.

With reference to FIG. 9, a dental porcelain colour chart is shown whichis divided into three main areas 130, 131 and 132, each subdivided intofour lines of seven subareas, several of the latter denoted by thenumerals 130a, 131a and 132a. The areas 130, 131, 132 display colourswith a predominantly red, yellow or blue hue respectively, the subareaswithin each main area displaying variations in the respective colourarranged in an ordered manner. In the chart shown, the hue increases instrength from left to right and in its degree of greyness (i.e. quantityof black pigment added) varies from top to bottom.

The chart of FIG. 9, with eighty-four different colours, was worked outto cover practically the entire range of colours found in natural teethbut it was subsequently found that certain colours, at the extremes ofthe three colour groups 130, 131, 132, were sufficiently rare to beomitted from the system. These extreme colours are shown in brokenoutline in FIG. 9 and, when omitted, reduce the number of subareas tothe more manageable number of sixty. These remaining subareas, shown infull outline, are each given an identification index, 11A/31H . . .37D/710X, corresponding to a respective dental porcelain colour.

It will be appreciated that, if only sixty colours are to be displayedby the buttons 101 in the system of FIGS. 7 and 8, not all the supportarms 104 will be used. In order to keep these colours in the orderedarrangement shown in the chart of FIG. 9, it is preferred to providegroups 126 with only two or three arms 104, as appropriate, rather thanto provide a smaller number of the groups 126, each with four arms 104.These groups 126, with two or three arms 104, may be preformed as suchbut, to simplify manufacture, identical groups of four arms arepreferably formed and the unwanted arms are then cut away.

It should be noted that, with the system of FIGS. 7 and 8, although thearm groups 126 overlap each other in their stored position, so that thestored system is very compact, all the buttons 102 are in fact visibleso that a dental surgeon can easily select buttons for matching with apatient's tooth, in use.

With reference now to FIG. 10 of the drawings, this shows additionalporcelain beads 201, 202, 203 and 204 which can be incorporated in anydental porcelain colour matching system for estimation of theenamel-dentine ratio of natural teeth. The beads 201-204 are generallytooth-shaped and are formed from an opaque dental porcelain base 205with a covering of translucent enamel 206 to simulate the underlyingdentine layer and overlying enamel layer respectively of natural teeth.

In the bead 201, the opaque base 205 has the shape of a young, unwornincisor tooth, with a ridged cutting edge 207 and a thick covering ofenamel 206, whereas in the bead 204, the porcelain base 205 has thesmooth cutting edge 208 of a very worn tooth and the enamel 206 formsonly a thin layer on the upper and lower surfaces and side edges. Thebeads 202 and 203 represent stages in tooth wear intermediate those ofthe beads 201 and 204, the bead 202 having a slightly ridged cuttingedge 207 with enamel 206 just filling the gaps between the ridges, andthe bead 203 having a smooth cutting edge 208 but a thicker coating ofenamel than the bead 204. Beads simulating further intermediate degreesof wear may be added to the beads 201-104.

It will be appreciated that the beads of FIG. 10 may be incorporated inany dental-porcelain colour matching system, such as those describedabove, either on the same support as coloured beads in the system, or ona separate support, and may be used to assist a dental surgeon toestimate the enamel-dentine ratio of a patient's natural teeth so thatthis can be simulated in a dental prosthesis.

The similitude of a prosthesis to natural teeth may be even furtherenhanced by the careful selection of the colour and degree oftranslucency of the enamel layer. This selection may be facilitated bythe incorporation of further beads in a system of the invention todisplay different types of enamel. For example, four beads similar tothe beads 201 may be used, but with enamels varying from verytranslucent to nearly opaque. A further four beads, like the beads 201,may display different coloured enamels: white; white-blue; blue; andblue-grey.

What is claimed is:
 1. A set of dental porcelain beads for incorporationin a dental-porcelain color matching system, each said bead comprisingan opaque dental-porcelain base in the shape of an incisor tooth with acoating of translucent enamel, at least some of said bases having theshape of the dentine layer of an unworn natural incisor tooth with aridged cutting edge, at least some of said bases having the shape of thedentine layer of a worn incisor tooth with a smooth cutting edge, and atleast some of said bases having the shape of the dentine layer in one ofthe successive stages between that of an unworn natural incisor toothand a worn incisor tooth, and said enamel coatings varying in thicknessso as substantially to simulate the enamel layer of the correspondingnatural tooth.
 2. A dental-porcelain color matching system comprising aplurality of dental-porcelain beads of different colors carried on asupport adapted to allow at least some of said beads to be moved apartso that each said bead can be placed individually against a patient'snatural tooth for color comparison with that tooth without colorinterference from any other bead on said support, wherein said supportcomprises an elongate body part with a stepped surface and a pluralityof respective pivot points, the arms projecting from a respective saidpivot point in a common plane and each arm carrying a said bead at itsfree end, wherein each said group is pivotally attached at its pivotpoint to a respective step of said stepped surface such that said groupslie in planes parallel to said steps and overlap each other in a storedcondition of the system so that the beads are closely spaced but all arevisible, and wherein each group is pivotable in its plane into aposition for said color comparison.
 3. A dental-porcelain color matchingsystem comprising a plurality of dental-porcelain beads of differentcolors carried on support adapted to allow at least some of said beadsto be moved apart so that each said bead can be placed individuallyagainst a patient's natural tooth for color comparison with that toothwithout color interference from any other bead on said support, whereinsaid support is made from a material selected from flexible andflexibly-resilient materials to allow beads which are closely spaced ina relaxed condition of the support to be moved apart for said colorcomparison.